Furling systems for the jibs and other headsails of sailboats are well known and widely used. The most common of these furling systems involves three basic components: (1) a luff extrusion, which runs along the forestay of the boat, and which holds the luff of the sail; (2) a drum or wheel mounted on the bow of the sailboat, used to “wind up” the sail about the extrusion; and (3) a swivel bearing mount which can slide along the top of the extrusion, and which allows the halyard to hold the sail up while permitting the extrusion to rotate at its top end relative to the forestay.
This prior art embodiment may be seen in FIG. 2. The tabling of the luff 16 of the jib l4 is sewn around and seized to the luff rope 1. The drum 26 rotatably attaches the bottom of the extrusion to the bow 30 of the boat. At the top of the extrusion the swivel 24 allows the luff wire or rope to rotate with respect to the halyard 12, which is directed through the masthead 88, and then back toward the deck of the boat.
Recent innovations in sail design have included the so-called “Code Zero” asymmetric headsail. The code zero is a free-flying sail, useful at apparent wind angles of between 40 and 65 degrees APP (apparent wind angle). These sails fill a niche between the Genoa jib and spinnaker, and have become popular with cruising sailors as well as racers.
Code zero sails generally contain their own furling systems, known as Code Zero Furlers, since Code Zero sails may be repeatedly set and struck during a single sail or race. FIG. 1 shows a typical prior art Code Zero Furler. These furlers differ from the older prior-art furlers in that they do not use luff extrusions, but rather use a luff wire, sewn into the luff of the sail in place of the extrusion. Because the luff wire does not have the torsional stiffness of the extrusion, Code Zero luff systems are not generally used as reefing systems. That is to say, these furlers are used either with the sail flying, completely unwound from the luff rope, or completely furled, with no sail area exposed.
The prior art Code Zero Furler may be understood by first referring to FIG. 1. A luff wire 9 is sewn into the luff of jib 1. At the lower end, or “tack” of the jib the luff wire is terminated with a lower eye 3, which is then affixed to furler wheel 2. At the upper end, or “head” of the jib the luff wire terminates in an upper eye 5, which is affixed, in turn to upper swivel 5, which in turn attaches to fitting 7. In many systems, the swivel is permanently affixed to the head of the jib, and the furler wheel is permanently affixed to the tack of the jib. When multiple headsails of this type are used, each contains its own swivels and furler wheels or drums, and these are generally of much smaller size and lighter weight than other types of prior art swivels and furler wheels.
Although FIG. 1 shows only a single headsail for the purpose of illustrating the principle, in practice Code Zero sails are often flown while another headsail is present, either flying or furled.
The use of a luff wire is dictated by the generally high-tension loads placed on the luff of the Code Zero headsails. The object of this feature is to reduce the sag of the forestay. These loads result from the large sail areas of these sails, from the full cut of the sails, and from the fact that these sails are usually mast-headed sails, running up to the very top of the mast 6, adding to the size of the sail.
The use of wire in the luff causes a number of problems, however. First, the wire is heavy, and awkward to handle. It does not bend easily and so the sail cannot be easily folded into a standard sail bag for storage.
A final problem involves the use of this Zero Code furling system for reefing the sail. Reefing differs from furling in that the former provides a reduced sail area under high wind conditions, where it is desirable to keep Zero Code sail aloft, but with the sail area reduced.
However, the steel cable does not have sufficient torsional stiffness to allow for reefing under high wind conditions. The foot of the sail, being subjected to higher tension due to the larger sail area at the foot, will twist the luff cable more than the head of the sail, leading to unacceptable sail deformation. However the present invention provides for the use of a lightweight rope of a much greater diameter than the heavier steel cable, so that a much thicker, and therefore stiffer rope cable can be used, with the possibility of reefing as well as furling.
A second departure of the present system involves the use of a novel furling drum, which contains a stop to take the pressure off the ball bearings themselves when subjected to excessive forestay tension. Ball bearings of the type used in the prior art for furler drums and wheels are most failure prone in tension mode, and Code Zero furlers are subject to tension forces far in excess of the other prior art furlers, due to the large sail area of Code Zero sails, and also due to the tendency of racing skippers to try to get the headsail luffs as tight as possible, thereby enhancing the aerodynamic characteristics of these sails. The use of the stop in the ball bearing mechanism provides a safety margin, so that when the furler is over-stressed the bearings will not fail, but will simply stop turning. If the bearings lock up in this way, and the sail needs to turn, as when coming about, the halyard need only be slackened momentarily to permit the turn, and can then be tightened down again.